The present invention relates to a cylindrical helical compression spring of the type formed from a wire or rod having a circular cross section whose ends are supported against spring discs.
Helical compression springs are known in which the wires or rods employed for their manufacture have a constant circular cross section over their entire length. The end windings of these springs are particularly in danger of breaking, mainly at those points where they lift off from the spring discs. At these points, which in theory constitute the clamping points of the helical spring, there occur, during use, rolling and friction movements between the end windings and the spring discs. After a short time these movements destroy the corrosion protection layer of the spring wire and its outer layer, which has been reinforced by shot peening and loaded with internal pressure stresses.
If the end windings of helical vehicle chassis springs are designed according to DIN (German Industrial Standard) 2096, page 1, FIG. 3, and spring discs as shown in part 2 of this standard, at page 2, FIG. 1, are used the end winding unavoidably come into contact with the immediately adjacent highly stressed spring active windings not only when the theoretical blocking force of the spring has been reached but already at lower forces which still lie in the operating range of the spring. This also produces the already mentioned damage to the wire surface and additionally the contact between windings produces noise. The main cause of the early contact between the windings in the prior art springs is a heavy deformation of the end windings which, only in theory, are considered to be rigid.